Great stuff. Thanks for the information. I always knew there was liquefaction going on at the base of Greenland's ice and I assumed geothermal, but I wasn't sure why it didn't create more of a problem. I half expected the ice sheet to turn into a giant slushy and slip into the ocean, given the cracks and fissures in the sheet that reach to the bottom.

I always thought it would be a great James Bond film plot, foiling a plan to melt the Greenland sheet via a thermonuclear warhead buried at the base in the center of the sheet. Preposterous, but so are all of those film plots.

It's almost as if we don't understand all the various forcings that could contribute to temperature fluctuations... fascinating.

Luckily we do understand the mayor forces... and scientific progress renders that part of the forcing's that we do not understand less and less significant.

The point was that a forcing known but assumed to be insignificant turned out to be a major factor in the system. This is not the same as new high-resolution measurement making previously invisible variations visible.

It's almost as if we don't understand all the various forcings that could contribute to temperature fluctuations... fascinating.

Luckily we do understand the mayor forces... and scientific progress renders that part of the forcing's that we do not understand less and less significant.

To be fair, we believe we understand the major forces. Not taking a side either way, but saying that we understand the important ones and the other ones don't matter as much is pretty short sighted. It may be true, but there isn't evidence to say it is.

Because the models of ocean level rise are tied to the rate that the ice sheets move into the ocean. That is partially a result of water on the base of the glacier. Apparently part of that water comes from internal heat, which had previously not been factored into the model (per the article). The rest comes from surface melt, then it penetrates the ice through shafts, termed moulins. This water at the base of the glacier acts as a lubricant increasing the speed of the glacier downhill. The faster the glacier hits the ocean the faster the ocean levels rise. If you live in Venice, the Netherlands, or South Florida that rate might be useful to know.

Climate scientists might have thought geothermal factors were insignificant. Most geologists that I know would read this and say, "Duh". We don't fully (or really even very much) undertand the forces inside the earth, but we have a pretty good feel for their magnitude. There are about a trillion cubic km of hot stuff moving around under the crust. That's not insignificant.Hence the value of multidisciplinary teams.

Because the models of ocean level rise are tied to the rate that the ice sheets move into the ocean. That is partially a result of water on the base of the glacier. Apparently part of that water comes from internal heat, which had previously not been factored into the model (per the article). The rest comes from surface melt, then it penetrates the ice through shafts, termed moulins. This water at the base of the glacier acts as a lubricant increasing the speed of the glacier downhill. The faster the glacier hits the ocean the faster the ocean levels rise. If you live in Venice, the Netherlands, or South Florida that rate might be useful to know.

Has the internal heat increased recently? If not, then it shouldn't change the speed that the glacier is moving, right?

Because the models of ocean level rise are tied to the rate that the ice sheets move into the ocean. That is partially a result of water on the base of the glacier. Apparently part of that water comes from internal heat, which had previously not been factored into the model (per the article). The rest comes from surface melt, then it penetrates the ice through shafts, termed moulins. This water at the base of the glacier acts as a lubricant increasing the speed of the glacier downhill. The faster the glacier hits the ocean the faster the ocean levels rise. If you live in Venice, the Netherlands, or South Florida that rate might be useful to know.

Has the internal heat increased recently? If not, then it shouldn't change the speed that the glacier is moving, right?

Not necessarily. If you don't account for the differential lubrication and unloading then you would probably be off on your movement models. The inflow of cold fresh water also needs to be accounted for.

Because the models of ocean level rise are tied to the rate that the ice sheets move into the ocean. That is partially a result of water on the base of the glacier. Apparently part of that water comes from internal heat, which had previously not been factored into the model (per the article). The rest comes from surface melt, then it penetrates the ice through shafts, termed moulins. This water at the base of the glacier acts as a lubricant increasing the speed of the glacier downhill. The faster the glacier hits the ocean the faster the ocean levels rise. If you live in Venice, the Netherlands, or South Florida that rate might be useful to know.

Has the internal heat increased recently? If not, then it shouldn't change the speed that the glacier is moving, right?

Not necessarily. If you don't account for the differential lubrication and unloading then you would probably be off on your movement models. The inflow of cold fresh water also needs to be accounted for.

That part I understand (as well as my old brain will let me), but I don't understand how internal heat changes the models *if* internal heat hasn't changed (do we even measure that?). I mean, if internal heat has stayed the same for x amount of years, wouldn't that just be considered a constant? Sort of like:

Total fresh water glacier is gliding on = ZFresh water supplied by internal heat melt = YFresh water supplied by other melt = X

Gives us:

X + Y = Z

If Z is increasing, and Y is a constant (if internal heat hasn't changed), then X must be increasing at a rate equal to the increase in Z?

Eventually; but the rate of recovery after the ice sheet goes away is really slow. ex northern England is rebounding upward at a rate of 10cm/century; southern England is dropping at half that rate (the crust tilts instead of just sinking where the ice is on top).

Peak values are 180 cm/century up in the middle of Canada, and down by 60 cm/century in the sea between Canada and Greenland.

Total fresh water glacier is gliding on = ZFresh water supplied by internal heat melt = YFresh water supplied by other melt = X

Gives us:

X + Y = Z

If Z is increasing, and Y is a constant (if internal heat hasn't changed), then X must be increasing at a rate equal to the increase in Z?

Trust me, it sounds right in my head.

The problem is that it is not as simple as that. Yes, it seems to make sense that the heat flux from the mantle would be fairly constant over all. However, the amount of water we estimate that melts and the amount of liquid water we estimate that is under the sheets is probably not thoroughly measured. Hard to get instrumentation under there. Instead we make some measurements and build a model to understand the rest of it. If that model did not properly account for internal heat, it would be off. The amount of water probably also changes other factors like rate of melt, etc.

It's almost as if we don't understand all the various forcings that could contribute to temperature fluctuations... fascinating.

Luckily we do understand the mayor forces... and scientific progress renders that part of the forcing's that we do not understand less and less significant.

To be fair, we believe we understand the major forces. Not taking a side either way, but saying that we understand the important ones and the other ones don't matter as much is pretty short sighted. It may be true, but there isn't evidence to say it is.

Yeah but tell that to all the people crying about how humans are primarily causing global warming.

Quote:

Thus, scientists who hope to understand the dynamics of the polar ice sheets—and thus the future of Earth’s ocean levels—cannot ignore the underlying geology.

The future of Earth's ocean levels are in the past. They were already much higher than they are now. It's a concept called a "cycle". It's been happening long before humans ever plagued the planet.

The real question is when the Earth hits it's apex of temperature adjust during this 'warming" period - does it then remain warm ? Or does it cool off again heading for another Ice Age ? We won't be around to find out (save for time travel) as this will occur several hundred thousand years from now. And if it remains warm (in effect breaking the thermostat) can we then at that time conclude that it was in fact human intervention ?

Hell - the State of Florida in the US has been several thousand feet underwater several times in it's 300+ million year history. Most of the State is made up of sediment deposited during previous sea level rises.

And somehow people really think we're going to stop this from happening again ?

Total fresh water glacier is gliding on = ZFresh water supplied by internal heat melt = YFresh water supplied by other melt = X

Gives us:

X + Y = Z

If Z is increasing, and Y is a constant (if internal heat hasn't changed), then X must be increasing at a rate equal to the increase in Z?

Trust me, it sounds right in my head.

The problem is that it is not as simple as that. Yes, it seems to make sense that the heat flux from the mantle would be fairly constant over all. However, the amount of water we estimate that melts and the amount of liquid water we estimate that is under the sheets is probably not thoroughly measured. Hard to get instrumentation under there. Instead we make some measurements and build a model to understand the rest of it. If that model did not properly account for internal heat, it would be off. The amount of water probably also changes other factors like rate of melt, etc.

It get's even more complicated than that: if current average temperatures are counteracting the heating somewhat, what happens when they are no longer sufficiently low to do so? like anything in balance, when you move beyond a certain tolerance of change on one side of the scale, changes on the other side can be rapid and violent.

That part I understand (as well as my old brain will let me), but I don't understand how internal heat changes the models *if* internal heat hasn't changed (do we even measure that?). I mean, if internal heat has stayed the same for x amount of years, wouldn't that just be considered a constant? )

OK, try this analogy: You leave home on your vacation, but when you get a few blocks away from your house, you suddenly realize you left the stove turned on. Do you think to yourself "The house wasn't on fire when I reached the end of the driveway, and the stove was on then, so everything will be fine when I get back next week," or do you have to consider that a revision to the model may require turning around to deal with the situation?

It's almost as if we don't understand all the various forcings that could contribute to temperature fluctuations... fascinating.

Luckily we do understand the mayor forces... and scientific progress renders that part of the forcing's that we do not understand less and less significant.

To be fair, we believe we understand the major forces. Not taking a side either way, but saying that we understand the important ones and the other ones don't matter as much is pretty short sighted. It may be true, but there isn't evidence to say it is.

Yeah but tell that to all the people crying about how humans are primarily causing global warming.

I did. I'm not sure what your overly confrontational attitude is supposed to accomplish, but if your goal was to insult anyone who disagrees with your "opinion" I dare say you succeeded.

Thus, scientists who hope to understand the dynamics of the polar ice sheets—and thus the future of Earth’s ocean levels—cannot ignore the underlying geology.

The future of Earth's ocean levels are in the past. They were already much higher than they are now. It's a concept called a "cycle". It's been happening long before humans ever plagued the planet.

The real question is when the Earth hits it's apex of temperature adjust during this 'warming" period - does it then remain warm ? Or does it cool off again heading for another Ice Age ? We won't be around to find out (save for time travel) as this will occur several hundred thousand years from now. And if it remains warm (in effect breaking the thermostat) can we then at that time conclude that it was in fact human intervention ?

Hell - the State of Florida in the US has been several thousand feet underwater several times in it's 300+ million year history. Most of the State is made up of sediment deposited during previous sea level rises.

And somehow people really think we're going to stop this from happening again ?

Poor Polar Bears.

Yes, and in geologic timescales, the recent changes in temperature and sea level are just rounding error. The difference is that this time around, someone plopped densely-populated metropolises at the coastlines and concentrated foodstocks into a relatively limited set of plants, and together these are far more sensitive to climate changes than past inhabitants of the planet.

One policy direction is to spend enormous amounts of effort trying to nudge the changes ever so slightly and hope that existing systems can continue... or we could try to harden our perch on this planet so as not to act frightened by every little fluctuation.

Neither approach is going to work in isolation, and nothing is going to work if policy doesn't make some attempt at synergy between the two. Having the US government come in and rebuild flood-damaged homes in the same flood-prone areas over and over again seems pretty stupid. And tossing the whole economy back into the Stone Age via regulation isn't an answer either because (1) temperatures are rising anyway and (2) no one expects all countries to comply.

Total fresh water glacier is gliding on = ZFresh water supplied by internal heat melt = YFresh water supplied by other melt = X

Gives us:

X + Y = Z

If Z is increasing, and Y is a constant (if internal heat hasn't changed), then X must be increasing at a rate equal to the increase in Z?

Trust me, it sounds right in my head.

The problem is that it is not as simple as that. Yes, it seems to make sense that the heat flux from the mantle would be fairly constant over all. However, the amount of water we estimate that melts and the amount of liquid water we estimate that is under the sheets is probably not thoroughly measured. Hard to get instrumentation under there. Instead we make some measurements and build a model to understand the rest of it. If that model did not properly account for internal heat, it would be off. The amount of water probably also changes other factors like rate of melt, etc.

Ah, okay, I've got it now. I was under the impression that we knew how much water (give or take a few gallons) was under them. Thanks for breaking it down.

Eventually; but the rate of recovery after the ice sheet goes away is really slow. ex northern England is rebounding upward at a rate of 10cm/century; southern England is dropping at half that rate (the crust tilts instead of just sinking where the ice is on top).

Peak values are 180 cm/year up in the middle of Canada, and down by 60 cm/year in the sea between Canada and Greenland.

I may be wrong ... but is not the scale in the map referenced to in mm per year?; i.e. the largest rise is 18 mm/year (which is really a lot)? 180cm/year sound way,way too much - in 100 years (which is geologically a very short time) the land would rise 180 meters ...

Eventually; but the rate of recovery after the ice sheet goes away is really slow. ex northern England is rebounding upward at a rate of 10cm/century; southern England is dropping at half that rate (the crust tilts instead of just sinking where the ice is on top).

Peak values are 180 cm/year up in the middle of Canada, and down by 60 cm/year in the sea between Canada and Greenland.

I may be wrong ... but is not the scale in the map referenced to in mm per year?; i.e. the largest rise is 18 mm/year (which is really a lot)? 180cm/year sound way,way too much - in 100 years (which is geologically a very short time) the land would rise 180 meters ...

oops. I copied the original values and didn't fully update the units after converting them to cm/century to be consistent with the values I'd written above.

This article makes sense. The earth's inner heat is several millions of degrees hot. One of the major prophets of Climate Change, previously known as Global Warming, told me so. See the Book of Gore, circa 2009.

This article makes sense. The earth's inner heat is several millions of degrees hot. One of the major prophets of Climate Change, previously known as Global Warming, told me so. See the Book of Gore, circa 2009.

No. The Earth's core is 10K degrees, close to the Sun's surface temperature.

Because the models of ocean level rise are tied to the rate that the ice sheets move into the ocean. That is partially a result of water on the base of the glacier. Apparently part of that water comes from internal heat, which had previously not been factored into the model (per the article). The rest comes from surface melt, then it penetrates the ice through shafts, termed moulins. This water at the base of the glacier acts as a lubricant increasing the speed of the glacier downhill. The faster the glacier hits the ocean the faster the ocean levels rise. If you live in Venice, the Netherlands, or South Florida that rate might be useful to know.